Windshield wiper motor



Feb. 3, 1953 F. SPRAGUE ET A1.

WINDSHIELD WIPER MOTOR 2 SHEETS-SHEET l Filed oct. 17, 1949 N .1-0 fvwm s r v f wmkw NH ww @BAK NQ mmf m ,BQ MS Nm. wv mow m Mr w 1| @MMA Q1' R. .Q vm wwf Nw Y am. m :Il M QQ I l f K y ww 5MM/ NM NQ $5.. wm mw M N NW llmwl. R a. JS ww S Q3 u m QM R D N\ Q\\ CLc/Y wm wm. i NN wv m N EQ n Q wn Q um. Qu 3 Feb. 3, 1953 F. sPRAGUE Erm. 2,627,251

WINDSHIELD wIPER MOTOR Filed. oct. 17, 1949 2 sHEETs--SHEET 2 Patented Feb. 3, 1953 UNITED STATES PATENT OFFICE WINDSHIELD WIPER MOTOR Frank Sprague and Elton F. Nichols, Michigan City, Ind., assignors to Sprague Devices, Inc., Michigan City, Ind., a corporation of Indiana Application October 17, 1949, Serial No. 121,842

10 Claims. 1

This invention relates to improvements in windshield wipers, and more particularly to windshield wipers of the type adapted to be operated by a difference in pressure acting upon opposite sides of a shiftable member.

The primary object of this invention is to provide a device of this character which does not require the use of springs and in which all of the moving parts, including the reversing mechanism, are actuated by a difference in pressure of an actuating iiuid, such as air.

A further object is to provide a device of this character in which the number of moving parts or units is reduced to a minimum to facilitate simplicity of construction and assembly of the device.

A further object is to provide a device of this character which is simple in construction, in which the constituent parts are formed of castings and like units which can be fabricated quickly and inexpensively and in which the requirement for machined parts is reduced to a minimum and whose construction is inexpensive.

A further object is to provide a device of this character having a novel means for positioning the wiper and the motor parts when the device is not operating.

A further object is to provide a windshield wiper with wiper blade positioning means actuated by fluid pressure and requiring a minimum number of moving parts.

Other objects will be apparent from the following specification.

ln the drawings:

Fig. 1 is a longitudinal horizontal sectional view taken on line I-I of Fig. 2.

Fig. 2 is a transverse sectional view taken on line 2--2 of Fig. 3.

Fig. 3 is a fragmentary detail sectional View taken on line 3--3 of Fig. 2.

Fig. 4 is a part schematic View illustrating the parking or blade positioning means in one operative position.

Fig. 5 is a fragmentary view of the parking device is another operative position.

Referring to the drawings which illustrate the preferred embodiment of the invention, the numeral It) designates the housing of the windshield wiper which is preferably formed of two cup-shaped sections which are axially aligned and which are secured together with the edges at the open ends thereof abutting to form a joint I2. The cup-shaped sections are preferably cast or molded and are formed of right and left parts, as best seen in Fig. l, and each thereof includes a cylindrical portion I4 and an outer end wall I6 formed integrally and so shaped that the inner surfaces thereof at I8 are cylindrical adjacent the end Wall I6. The cylindrical surface I8 is preferably interrupted at its outer end portion by lugs I 9 and by a reduced diameter cylindrical portion 2B adjacent the open end thereof. The meeting end portions of the cupshaped housing members are transversely configured to substantially the form illustrated in Fig. 2 providing the transversely aligned bearing receiving portions 22, the substantially vertically aligned grooved gear-receiving portions 2li, and the front opening 26 at the central portion of the housing. It will be understood that mounting lugs 28 may be formed on the device if desired.

Each of the cup-shaped housing parts form one end of a substantially closed cylinder within which a piston may reciprocate with a substantially sealed or airtight lit. Each of the sections is lined by a preformed tubular member 3S which has a smooth inner surface facilitating the reciprocation of a piston therein responsive to differences in fluid pressure at opposite sides of the piston. As best seen in Fig.` 1, the preformed cylinders 3D are of a size and. shape to be positioned by lugs I9 at their outer ends and to nt snugly within the reduced diameter cylindrical or shouldered portions 20 of the cupshaped housing portions. The preformed cylin.- ders 30 preferably have a substantially airtight fit within said reduced portions 20, for example, a press lit. At the end of each preformed liner member 3c adjacent the center of the windshield housing is formed an out-turned flange 32 which bears against the shoulder of the housing por,- tion 2t facing the center of the housing. The length of the preformed tube or liner 30 is such that its opposite edge 34 terminates spaced from the adjacent end wall I6 of the housing. Consequently, the space within the liner 3U communicates with the substantially cylindrical clearance space 36 between the liner 30 and the cylindrical housing wall I4 and extending between the shoulder portion 20 and the outer end wall I6.

The portions 22 of the casing receive axially aligned bearings 38 within which is journaled transverse sleeve 40 which may be locked in place by split rings or any other means found suitable. The bore of the sleeve 40 at one end thereof` is preferably tapered at 42 so that the mouth of the sleeve at that end is of larger diameter than at its opposite end. The sleeve 40 mounts a shaft 44 which is adapted to carry the windshield wiper blade (not shown). The shaft tl has a snug fit therein and is congured to have a wedged t in said sleeve, as by the provision of a tapered portion i6 fitting within the tapered portion i2 of the sleeve. The shank 4t is held in place Within the sleeve by a screw whose shank t3 is threaded in an axial bore in the small diameter bore of the shaft lill and Whose head 5d is of a size to bear against the end of the tube having the small diameter bore. 'I'hus it will be ape parent that as the screw 48, 5@ is threaded into the axial bore in the end of the shaft 515, the margin of the head si] will bebrought into engagement with the left-hand end of.' the sleeve 40, as seen in Fig. 2, and thereupon continued rotation of the screw will draw' the shaft 4d to' the left and will bring the tapered parts @2, it

into wedging engagement. The parts are thus held for rotation Without slippage and are posif ti'oned in axial alignment by a single securing mea-nsf, namely screw ed; 50 which can be easily applied and released to facilitate assembly and disassembly of the structure. The-sleeve il@ nxedl-y mounts a gear' 52 atl its center which projectsV into thel longitudinal' groove 25 formed at the' top' of the casing in the top portion 24. It Willbe observed that the sleeve lill and the shaft M! are located above the axis of the. cylinder of the* housing;

A piston unit; which is preferably cast integral@I l'y; is received Within the housing and includes an elongatedrigid connector portion 5!! having integrally formed therewith a toothed rack 5e. The connector' portion 5d mounts end plates 53 at its' Opposite ends, which end plates are prei'L erably circular, are positioned transverse of the housing substantially concentric therewith and have clearance with the inner surface of the cylinder liners 30. The parts 5d, 56 and 5dv are preferably formed integrally, and the parts 5&3 and 56 are located eccentrically, as best seen in Fig; 2', so that the rack 56 may mesh with the gear- 52. A roller Gil is` journaled upon a pin or shaft'Z locked'v in a bore in the housing. The pin 62' intersects the groove 25 formed in the bottom` frame portion 213, and the rollerV t@ ilts Within said groove 25 With clearance and in such a` position that the'bottom surface of the rigid connector portion 5G bears upon said roller. The: rollerw Wis-preferably positioned directly below' the sleeve llt so that it will support the rack and; Connector 5:4; 56V at the-point' at which the gear 52- meshes with said rack. Alongside the Support 5d andv extendingl parallel thereto is a screw-threaded shaft 6'4- whose oppositel ends are carried by the-circular plates 53. Adjustabl'y mounted upon the threaded shaft or rod 54 are a pair of' internally screw-threaded stopmembers (lwhich` preferably'afre located equi-spaced from the" adjacent` end plates 53 but which may be positioned at anyselected point along the shaft 64and`in unbalanced relation, that is, the spacing oflon'eof the members 65 from the adjacent plateSBLmay be more or less than the spacing of th'eother stop E6 from the end plate 58 adjacent thereto. Fluid-tight pistons are mounted upon the members' 58; the same preferably including an inner plate portion-8, which bears at against the outerface of the part', a cup-shaped resient' niember'which may be formed of leather, rubber; plastic material orl the like, and an inner plate' 'l2Vv bearingV against and tting within the cup-shaped piston" member l0. The open ends ofV thecupeshapedrnembers 1li face outwardly,

'4 as seen in Fig. l. While this construction of piston is preferred, it will be understood that the pistons may be formed of any other construction found suitable and practical.

A valve body or block 'M is secured to the main body or cylindrical housing i@ to span and close the opening 26 of the latter. The valve body 'M is soshaped andcontouredthat itts against the body or' cylindrical housing- It, for which purpose it may be provided with lianges, ears or securing members to facilitate connection 0f the parts. Thus at the: bottom along its length, the valve body 'lll may have a flange It which bears flat against a portion of' the bottom surface of the body IKL. and at", its top the body 'lf3 may be provided with ears 'i3 adapted to bear against the housing iiiandtobe secured thereto as by screws Sii. The Vbody preferably has a lower cylindrical bore' E3244 lined by a preformed metal sleeve or tube ed and an upper cylindrical bore lined by a preformed metal tube or cylinder.' 88. End walls te close the. ends ofi the. cylinders denned bythe tubes Se and' 38, and a vent. s2 open to atmosphere is providedati eachend of the cyl, inder defined by the tube ed, sai'dlvents E21 preferably being formed in the end wallsJ 9&3, as shown in Fig.' 3. `Suitable gaskets (not shown) are pro'- vided. Where' required.

in intake' port is. openincommunication with? the bor'ei il? at substantially the center thereof, and a socket' @t is preferably formed integrally' with the valve body i4 in register with the @s is" adapted to receive have connected thereto a fluidA conduit line et; as best illustrated in Figi 4. The sleeve 8d is attened at itil, and said attened portion it is positioned in register with the port 9d to provide al passagel between the sleeve and the body extending the length off the flattened portion ist; Apertures or ports it and les are formed in the sleeve atl the opposite ends of the'l attened portion Eile.. Consequently, huid from' the line ils may enter into the sleeve or cylinder Se through the port 91%, the passage provided by the sleeve portion its and the ports til? and les which are preferably equi-spaced from and at opposite sides of the port 94; A valve rod 5% mounts a` plurality of cylindrical members or piston-like parts its, liti, H2 and ils in spaced? relation along its length. The members lill, llt and Hilare preferably similari-.y constructed, and each has a sealing t within the tube or cylinder te which prevents the leakage of fluid therepast. The members m3 and lift, positioned; at opposite ends of the rod it, are spacedv inwardly from said ends a slightV distance. The members lrliland il? are equi-spaced from the center of the rod me and are spaced apart a distance such that theoutermost surfaces thereof are spaced a distance less the spacing between the ports |532 and IM. The'shaft ist is shorter than the sleeve 85.-, and the difference of the lengths of these parts subtracted. from the spacing between the ports |02, le@ represents substantially the spacing or a spacing slightly greater than the distance between the outermost faces of the members HB and l i2.

rihe valve body M and the sleeve til are provided with registering elongated slots HB extending inwardly and opening at the cavity of the body it., as best seen in Fig. 2. The slot i It is of comparatively short length and slidably receives a pin l le havingone end thereof threaded in the rod itt substantially at the center thereof tobe xedly secured to said rod. The pin I8 mounts a head portion |20 which either bears against or slidably encircles the rod 54 between the heads 86. It will be apparent that as the piston unit 52, B4, 58, 10 reciprocates, one or the other of the two stops |56 thereof will come into engagement with the pin unit I I8, as said unit nears the end of a stroke and carries that pin structure and the valve unit, including the rod |05 and the cylindrical portions i, H0, ||2, therewith, through the elongated slots H8.

A plurality of ports provide communication between the interiors of the valve cylinders 84 and 88. Thus two ports |22, |24 establish communication between the opposite ends of the cylinders, said ports being spaced from the ends of the cylinders a distance slightly greater than the spacing between the inner faces of the memV bers |08 and from the adjacent end surfaces of the rod |08, as best illustrated at the left in Fig. 3. A second pair of ports |28 and |28 are located in substantially equi-spaced relation to the opposite ends of such cylinders and preferably are spaced apart a distance substantially equal to the spacing between the ports |82 and |84.

A rod or shaft |30 of substantially the same length as the rod or shaft |88 is received within the cylinder 88 and mounts a plurality of sealing members or piston-like parts |32, |3it, |33 and |38 which preferably correspond to the members |08||4 on the rod |05 in that each has a sliding, sealing fit within its tube or sleeve B8 to prevent the leakage of iiuid therepast. The outermost members |32 and |38 are mounted upon the shaft |88 with their outer faces spaced from the end of the shaft |30 a distance greater than the spacing of the ports |22 and iZt' from the ends of the cylinders 84, 88, as best illustrated at the right in Fig. 3. The members |3I3 and |38 are mounted on the shaft |33 in equispaced relation to the center thereof and prefer ably are spaced apart substantially the same dimension as the spacing of the members ||0 and ||2.

A port |40 is formed in the valve body '|13 and the sleeve 88 for communication between the cavity oi the housing i0 at a point outwardly of the reduced portion 20 at the right-hand end of the cylinder unit as viewed in l, and a second port |42 similarly constructed is provided in spaced relation thereto and communicates with the interior of the body i8 outwardly of the reduced cylindrical portion 28 at the left-hand side of said figure. The ends of these ports |88, |42, communicating with the cylinder 88, are preferably spaced substantially equally from the longitudinal center of the tube 88 at such a distance that one of the members |34 and |36 is always positioned between the ports or both members i3d and |33 simultaneously span and close said ports. An exhaust port |44 is formed in the tube 88 and the body T4, and a socket |48 registers therewith for connection of a line |48, as best seen in Fig. 4. It will be understood, however, that the line Hi8 need not be used in al1 instances and that the port |24 may provide a direct communication with atmosphere.

When the device has been assembled with the parts arranged as described and illustrated herein, fluid under pressure, such as air, is supplied thereto from the line 08 under the control of a manually operable valve, such as the valve |50. Assuming that the primary valve. including the parts |06| I4, is in the position illustrated in Fig. 3, air from the line 08 will enter the port 94, the passage |00 and the ports |02 and |84 into the spaces between the valve elements |08, ||0 and between the valve elements ||2 and H4. Air entering the port |02 is discharged from the cylinder 84 through the port |28 and enters the cylinder 88 between the pistons or valve members |32, |34 against which it acts equally and is rendered static. Air which enters the cylinder 84 at the port |04 is discharged therefrom through the ports |24 and |281. Air which enters the cylinder 88 through the port |24 acts upon the valve member or piston |38 and exerts a pressure causing movement of the same, its mounting shaft |30, and the other piston or sealing members |32, |34 and |36 mounted on said shaft, to the position illustrated in Fig. 3, the right-hand end of the shaft |30 bearing against the right-hand end wall 00 of the valve unit. In this position of the parts, air which enters the cylinder 88 from the port |28 passes to the bore |22. The bore |32 communicates `with the space between the cylinder sleeve I8 and the cylindrical wall I4 of the body at the left-hand end thereof, as viewed in Fig. l, thereby causing a pressure to be applied to the outer surface of the left-hand piston in Fig. 1 to cause movement of the piston unit and associated parts to the right, as viewed in Fig. l. During this stroke the air at the outer end of the right-hand cylinder, which is pushed by the right-hand piston 18, is discharged from that cylinder through the port |20 and thence through the port |48, which, being positioned substantially centrally of the length of the.` cylinder 88, is in free communication with the port H58.

It will be apparent that as the piston unit approaches the end of its stroke toward the right, as viewed in Fig. l, the left-hand nut 66 comes into engagement with the pin |28 carried by the stem |06 of the primary valve and moves that pin and the valve stern to the right, as accommodated by the slot IIS, to the position illustrated in Fig. 4. Thereupon the air which enters the port |82 is divided and permitted to enter the ports |22 and |28. The air entering the port |22 acts upon the outer end of the piston or sealing member |32 and moves the shaft or rod |38 and its sealing members |32,

|34, |35 and |38 to the left, that is, to the position illustrated in Fig. 4.

The pressure responsive movement of the secondary valve units |30|38 to the left causes pressure in the cylinder 88 on the left of the sealing member |88 to be exhausted through the port |24, the left-hand end of the cylinder 85, and the leit-hand vent port 82. Thus the movement of the shiftable parts |i|8| it of the primary valve member serves to control the ow of fluid for the purpose of positioning the shiftable parts |30|38 of the secondary valve to exhaust the pressure condition previously existing at one end of said secondary valve and to supply fluid under pressure at the opposite end of the device to thereby change the setting of the secondary valve.

In the position of the valves illustrated in Fig. 4, luid entering the cylinder 84 at the port |02 is discharged through the port |28 into the cylinder 88 between the seals |32 and |34 which have now been so positioned as to open the port |40 into communication with the port |26. Fluid under pressure thus is supplied to the righthand'. cylinder to cause' the lpistoriunit to be shiftedv to the leftVV as Viewed in Fig. 1. The fluid at the: left-hand: end of the cylinder displacedl byv the left-hand piston is exhausted through: the port M2 which has been: placed in communication` with the port |86 as seen in Fig. 4; The strokev or movement of the pistonr to the left continues until the. rightehan'd abutment 6@- hasV engaged the pin I2@ and moved the samel andV the shiftable elements i-l l of. the primary valve from the Fig. 4 position to the Fig. 3` position, thus setting up a` reverse flowpath for fluid, and particularly a flow path between the ports lil@ and |26 at the left-hand end of the unit, and a now path between the port |22 and the right-hand vent port 92.', which causes.y the huid'` pressurevv to return. the shiftable elements ld- |38 of the secondary valve to the 3` position..

It will be observed that the number of moving parts of this device is small, the. same being arranged in units and constituting the' shiftable parts of the primary valve as one unit, the shiftabie parts of the secondary valve as a second. unit, the piston, the connecting rack and the'rod Eli as a third unit, and the shaft Lid, sleeve 46 and gear 52 as the fourth unit. None of the moving parts arer subject to or under the influence of springs, and all of the parts are positively operated either mechanically or, in the case of the elements of the secondary valve, by fluid pressure. This feature of the construction results in simplicity of manufacture and assembly, reduction in cost, and efcient and trouble-free operation.

Another advantage of this construction is the fact that thestroke of the pistons may he controlled easily and through a wide change of adjustment. ThisV adjustment is eifected by simply changing the position of one or both of the abutment members (it so as to control the time at which the abutments engage and shift the nger 12) andk the shiftable valve elements of the primary Valve during the course of the stroke of thev device. It will be observed that as the space between the abutments @S is reduced, the amplitude of the stroke of the pistons will he reduced. Similarly, as the spacing between the abutments is increased, the amplitude of the stroke will be increased, subject to the limitation that the parts may not be spaced so far apart that an abutment will fail to engage and shift the pin before theV piston reaches the full end of its operative stroke or movement within the cylinder housing.

Another' adjustment which is possible is to position the abutments so that the spacing between one thereof and the piston adjacent thereto is different from the spacing between the other and the piston adjacent to the other. This Will serve to change the location of the segment or arc through which the shaft iii rotates. In this connection it will oe observedV that the gear 52 is large and has a number of teeth so related to the number of teeth upon the rack 55 that the shafts @I4 willv normally operate through a segment or stroke of less than 18() degrees. The various adjustments mentioned facilitate the application of the windshield wiper to Vehicles of different structural characteristics.

A desirable feature of any windshield wiper is the provision therein of means for parking or positioning the windshield wiper blade at an end of' its stroke so that it is out of the line of Vision of the operator when not in use. Means for accomplis'hing this result are illustrated in Figs. e' and 5. This means' constitutes the differential Valve unit |52 which is interposed in the system betweenv the control valve |5 and the pressure source |55 on the one hand; and the conduits 98 and 158 on the other hand. This diiferential pressure valve comprises a housing having at one end a small diameter cylindrical bore |56, and at its opposite end a bore E58 of larger diameter. A line |63 connects the iiuid pressure source [5d with the end of the cylinder bore |56, said connection being eifected at an opening |82 in the end wall of the Valve |52 at the outer end of the small diameter chamber thereof. A line |65 connects the source of pressure with the valve |563. A line |66 connects the valve I5@ with the large diameter cylinder bore |58 at a port i553 in the end. wall of the valve |52.

A valve unitis shiftable Within the valve housi ing |52 and includes a sealing member or' piston i7@ shiftable in and havingV a sealing slide fit within the small bore portion |525- of the cylinder; AA second piston or sealing member 772 is shiftabl-e in and has a sealing t within the large diameter cylindrical portion i 53. A rigid rod 773 iXedly connects the pistons i7@ and |72 in predetermined spaced relation. The parts are so arranged that when the valve l 5@ is open to permit uidunder pressure from the source |52 to pass into the large diameter cylinder bore |58 simultaneously with the supply of fluid under pressure through line IS@ from the source to the small diameter bore of the cylinder, the difierence in area of the two pistons |72 and |175 will cause the piston unit to assume the position shown in Fig. 4, being at the end of its str-oke toward the small diameter end of the Valve housing |52. The line |63 is connected to the small diameter cylinder bore |56 intermediate its ends and at a port |75 so spaced and positioned from me end of the housing in which the port lez is formed that it exceeds the axial dimension of the piston member 70 and is open into full communieation with the cylinder bore when the valve parts and |72 are in their normal pressure dierence responsive position. A vent |78 1s formed in the differential valve housing spa-ced longitudinally thereof from the port |76 a distance greater than the axial dimension of the sealing member |70 and in such position that tne sealing member i7@ may be positioned between the ports Ii andv |78 when in the Fig. 5 position, for purposes to be described. The line 98 is connected to the valve at a port |33 inter-- mediate the length of the large diameter cylinder bore 758 and substantially centrally thereof so as to be fully opened when the sealing member |72 is in both its Fig. 4 and its Fig. 5 position.

Fig. 4 illustrates the normal operating position of the device in which the valve ii is open so that the differential Valve assumes the position shown in Fig. i due to the difference in area of the ltwo pistons ii and |72 against which pressure from the source |54 acts. The pressure in the line it@ acting against the piston 7h is static but the pressure passing' from source |547 through line Bild, valve |59 and line i enters the large cylinder bore |58 and is discharged therefrom through the port i8@ and ythe line 98 to the primary valve of the wiper motor. The fiuid under pressure which is exhausted through the port |54 of the secondary valve of the windshield wiper passes through line M8, port |76, the small cylinder bore |56 and the port |78 to atmosphere.

` As soon as the valve |50 is closed, however, thus stopping the supply of uid under pressure to the large diameter cylinder bore |58, the fluid under pressure passing through line |60 and acting against the small diameter piston |10 is eifective to shift the valve parts, |10, |12, |111 toward the large diameter end of the valve chamber to the position illustrated in Fig. 5. During this movement the piston or seal |10 will pass across the port |16 to assume a position between the ports |15 and |18, and the piston |12 will pass across the port |80 to assume a position between that port and the port |68. Thereupon the now of iiuid under pressure from the source through the two lines 98 and IliS is reversed, the line |48 becomes the inlet line to the wiper motor, and the line 98 becomes the outlet from the wiper motor. Fluid under pressure flows from source |54, line |00, through port |02 into the small cylinder chamber |5S, thence through ports |15 and conduit Hi8 to port iM of the secondary valve, When this occurs, assuming that the valve par-ts are in the position illustrated in Fig. 4, fluid under pressure will enter the valve port |42 and flow to the left-hand end of the cylinder as viewed in Fig. 1, thus causing movement of the piston toward the right. The duid which is displaced ahead of the right-hand piston incident to that movement to the right is exhausted through port |00 between the seals |32 and |34 and thence passes through the port |26 into the primary cylinder between the seals |08 and lli), and thence `passes out through port |02 to port 94 and the conduit 9B. Fluid pressure from conduit 98 enters the large chamber bore of the cylinder |58 above the piston |12, that is, in the space between the pistons |10, |12, and is exhausted through the vent |10 with which it is in open communication as seen in Fig. 5.

Inasmuch as the setting of the primary and secondary valves of the wiper motor, shown in Fig. 5, which existed at the time the valve |50 was closed, was such that for normal operation with the valve |50 open the piston would be caused to move toward the left, it will be apparent that the closing of the valve |50 causes a reverse flow of fluid under pressure and reverses the direction of movement of the pistons so that the pistons can move toward the right until the left-hand abutment 50 engages the pin |20. Since the stem |06 of the primary valve is in engagement with the end wall at the right-hand end of the unit, no movement of the valve is effected, and the engagement of the left abutment B0 with the pin |20 serves to stop the Vmovement of the pistons. Therefore, as long as any power is applied to the system thereafter while the valve |50 remains closed, that power or fluid pressure will be exerted in a direction to hold the device positively at one end of its stroke. Inasmuch as power is derived usually from a pump operated by the engine or motor of the vehicle whenever that engine or motor is actuated, there will be the application of power from fluid under pressure to the windshield wiper to either operate the windshield wiper or to position the windshield wiper at an end of its stroke at all times that the vehicle is in operation or in use.

One interesting attribute of the device is that the position in which the windshield wiper is parked will depend upon the position in which it was traveling, and more particularly, upon the position occupied by the primary and secondary valves, at the time the valve |50 is closed. Thus, if the valve |50 is closed while the primary and secondary valves of the windshield wiper occupy positions as illustrated in Fig. 3, then the piston unit which was set by said valves to travel toward the right will have its movement reversed and will travel toward and be parked at the lefthand end of its stroke.

Another interesting attribute is the fact that, regardless of the position at which the windshield wiper is parked the opening of the valve |50 will cause the operation of the windshield wiper to be resumed without diiiiculty or without manipulation other than the manual operation of the valve |50.

`While the preferred embodiments of the invention have been illustrated and described herein, it will be understood that changes may be made in the construction within the scope of the appended claims without departing from the spirit of the invention.

We claim:

1. A windshield wiper comprising a housing having a pair of fluid passages opening therein at opposed points and an opening at substantially midlength thereof, a pressure responsive drive unit oscillatable in said housing and including a pair of spaced pistons positioned at opposite ends of said housing and outwardly of said housing opening, means iixedly connecting said pistons, a valve casing secured to said first housing to span said opening and having a primary valve chamber parallel to said housing and a secondary valve chamber communicating with said housing passages, said valve casing having a slot establishing communication between said primary valve chamber and said housing opening, a primary valve element shiftable in said primary valve chamber and including a proJection extending through said slot and adjacent to said piston connecting means, spaced abutments carried by said piston connecting means and adapted to engage said projection, a secondary pressure-responsive valve element in said secondary valve chamber, said casing having an inlet, an outlet and a plurality or^ spaced passages connecting said valve chambers, said valves cooperating to control the ow of uid under pressure between said inlet and said outlet in diierent paths through said; passages and chambers to oscillate said drive uni 2. A windshield wiper as defined in claim 1, wherein said housing comprises a pair of :axially aligned cup-shaped members connected in communication.

3. A windshield wiper as defined in claim 1, wherein said housing comprisesa pair of axially allgned cup-shaped members connected in communication and has a cylindrical bore of enlarged diameter adjacent its opposite ends, and a pair of preformed tubes fit in the opposite enlarged ends of said bore anchored at their inner ends in the portion of the bore between said enlarged end portions and spaced from said housing at the enlarged diameter portions and at the outer ends thereof, said rst named passages opening into said bore at the space between the same and one of said tubes.

4. A windshield wiper as defined in claim 1, wherein each of said valves has a cylindrical bore and the control element thereof is of the spool type shiftable axially in said bore and including a plurality of spaced sealing members spanning said bore, said passages communicating with said cylindrical bores at spaced points.

5. A windshield wiper as defined in claim 1, wherein said housing is cylindrical and said valves are of the spool type and each has a cylindrical bore parallel to said housing and an axially shiftable spool having a plurality of spaced enlarged piston-like sealing portions.

6. A Windshield wiper comprising a housing having a pair of iiuid passages opening therein at opposed points, a pressure responsive drive unit oscillatable in said housing, a primary valve and a secondary valve cooperating to control iiow of fluid in said passages between an inlet and an outlet, said valves being connected by a plurality of spaced passages controlled by said primary valve, and means actuated by said drive unit at the end of each stroke for reversing said primary valve, said secondary valve including an element shiftable in response to the ilow pattern through said last named passages to control the flow in said rst named passages, and a control system including a manual control valve, a source of fluid pressure and a differential pressure valve interposed in said system to control the flow of iiuid in said system in response to the setting of said manual valve.

'7. A Windshield wiper comprising a housing having a pair of fluid passages opening therein at opposed points, a pressure responsive drive unit osoillatable in said housing, a primary valve and a secondary valve cooperating to control flow of uid in said passages between an inlet and an outlet, said valves being connected by a plurality of Aspaced passages controlled by said primary valve, and means actuated `by said drive unit at the end of each stroke for reversing said primary valve, said secondary valve including an element shiftable in response to the flow pattern through said last named passages to control the ow in said viirst named passages, and a fluid pressure network including a source of fluid pressure, a `manual control valve and a valve having a pair of opposed actuating pistons of different areas, said manual` valve being interposed in said system between said pressure source and the connection of the large area end of said last named valve in said system, whereby said last named valve controls flow in said system to and from said primary and secondary valves in one direction when' said manual valve is open and in a different direction when said manual valve is closed. 8. The combination with a pressure responsive windshield wiper motor having a plurality of uid passages terminating in a pair ofpcrts and controlled by valves responsive to the operation of said motor, o-f a fluid pressure network connected at said ports and including a positioning valve, said positioning valve controlling the direction of flow of fluid through said motor and including a housing provided with a pair of cham.- bers of different cross-sectional sizes and a shift able valve element including spaced connected piston members slidable in different valve chambers, a manual valve, a source of fluid under pressure, and lines connecting said pressure source with opposite chambers of said positioning valve, said manual valve being interposed in the line leading to the large area chamber of said positioning valve.

9. The combination with a pressure responsive windshield wiper motor having a plurality of iluid passages terminating in a pair of ports and controlled by valves responsive to the operation of said motor, of a pair of conduits connected to said ports, a positioning valve including a chambered housing having a rst set of spaced ports connected to said conduits and a shiftable valve element, said positioning valve having a vent between said first ports adapted to communicate with a selected one of said rst ports according to the setting of said valve element, said valve element having a second set of spaced ports and being responsive to fluid pressure, and iiuid pressure control means connected to said positioning valve at said second set of ports.

1,0. rIhe combination with a pressure responsive windshield wiper motor having a plurality of iiuid passages terminating in a pair of ports and controlled by valves responsive to the operation of said motor, of a uid pressure network connected at said ports and including a pressure controlled reversing valve for controlling thepath of flow of iiuid to and from said ports and motor, and a manual control valve in said network actuable to control the setting of said reversing valve.

FRANK SPRAGUE. ELTON F. NICHOLS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 663,135 Spencer Dec. 4, 1900 896,571 Ocain Aug. 18, 1908 968,861 Lindstrom Aug. 30, 19110 '1,363,333 4,Lower Dec. 28, 1920 1,674,056 Oishei et al. June 19, 1923 1,694,279 Oishei Dec. 4, 1928 2,263,003 Koppelman Nov, 18, 1941 

